Turbocharger Impellers Research Articles

ANALYSIS OF DESIGNS, MODELS AND METHODS OF STUDYING THE DYNAMICS OF HIGH-ROTATION ELEMENTS OF TANK ENGINES (REVIEW ARTICLE)

A lot of problems arise when tank engines are equipped with high-speed elements. They are related to the need of analyzing the stress-strain state and critical modes of rotation of these elements. For that reason, it requires an in-depth analysis of requirements and constructive solutions of engines and their high-speed elements. Moreover, modern studies of engine dynamics attract attention. Attention should also be paid to the analysis of existing designs of turbocharging systems of tank engines. It is important to analyze the models and research methods of the static and dynamic stress-strain state of turbocharger impellers as well. The analysis of problem aspects has been carried out and it is possible to note that for now the problem of studying the stress-strain state and critical modes of rotation of high-speed elements of tanks and engines for armored vehicles does not have a complete solution. We need new approaches, models and research methods and tools that create a basis for substantiating progressive technical solutions. Keywords: armored vehicles; tank engines; turbocharger; high-speed elements; stress-strain state

Applying CFD simulation program to analysis characteristic of turbocharger’s impeller of marine diesel engines

Marine diesel engines use centrifugal compressors as the impellers to supercharge and it is driven directly by exhaust gas turbines. The working process of the impeller is a combination of changing parameters and thermodynamic processes inside the impeller. The technical and environmental conditions of the impeller will greatly affect the working characteristics of the engine. Nowadays, the technology of simulation and calculation of fluid and gas flow dynamics (CFD) is developing and is widely applied in many fields of ships and industry. We propose to research and apply CFD techniques to analyze and simulate the working process of turbocharger impellers for marine diesel engines. The marine diesel impeller CFD simulation program is used to analyze the thermodynamic processes of the impeller and graphically simulate the working states of the impeller at different operating speeds. In this paper, we are using the experimental results to analyze the processes of the Mitsubishi impeller model MET42SC type DA3G installation on M/V VTB BRAVE to verify the simulation results.

Reverse engineering and performance analysis of a small-scale centrifugal compressor impeller

Analysing the performance of centrifugal compressors can be a time-consuming process, depending on the direction from which the problem is approached: conventional or reverse. For devices such as micro gas turbines (MGTs), the methodology of design often involves taking existing components (e.g., turbocharger impellers) and modifying them to fit into an MGT assembly. The reengineered design is analysed aerodynamically and structurally to predict the performance of the design under normal operating conditions. To achieve this, the reengineered design must be virtualised using methods of reverse-engineering. The purpose of this project was to compare two methods of virtualisation and to evaluate the performance of the resulting CAD models based on CFD calculations and experimental measurements. The ultimate goal was to determine which of the two methods would deliver the best solution in future virtualisation projects.

Simulation on the Thixocasting Process of the Turbocharger Impellers and Selection of the Viscosity Models

The thixocasting technology is chosen to produce the turbocharger impellers as it is capable of producing castings with high precision dimension, free of oxide and shrinkage porosity defects and therefore long service life. The thixocasting turbocharger impellers have the similar mechanical property to those produced by forging and machine processes, but much less costs. In the thixocasting process, the semisolid slurry with certain solid fraction is injected into mould at a high speed. Since high viscosity and thixotropic characteristics, the semisolid slurry reveals unique flow condition and characteristics in the filling process. So, its very desirable for the die design, process optimization, and defect control to visualize the high-speed filling process of semisolid slurry by numerical simulation. In this paper, several commonly used viscosity models for semisolid slurry are analysed. The Power law cut-off model (PLCO) model is selected to simulate the filling process in the thixocasting process of the impellers of 319s alloy, compared with actual results by partial filling testing. The causes of the casting defects are also analysed, indicating that the simulation results can accurately reproduce the filling process of semisolid slurry, and PLCO model is a successful choice for simulating the filling process of semisolid slurry with high solid fraction.

Effect of Casting Size on Microstructure and Mechanical Properties of Thixocastings

A general rule in conventional liquid metal casting processes is that smaller size would produce better metallurgical quality and mechanical properties. The conclusion that semi-solid thixocasting process doesnt follow this rule has been made recently. The microstructure and mechanical properties of semi-solid thixocastings are much less dependent on casting size and cooling rate than the liquid castings. The step casting in the previous study is specially designed and simplified. The practical castings, e.g. turbocharger impellers, are more complex than the step castings. In this work, the turbocharger impeller is used to study the impact of section size representing the casting size on the microstructure and mechanical properties of semi-solid thixocastings, compared with the step casting. Section thickness decreases from 50 mm to 3.5 mm. In addition, the impact of casting thickness on the eutectic phase is also presented. The results reveal that the size of primary α-Al particles is insensitive to the casting thickness in semi-solid thixocasting. The cooling rate has a notable impact on the size and geometric characteristics of the eutectic silicon particles, but the impact is reduced by the following T61 heat treatment. The association between the casting thickness and casting defects is discussed, in order to further understand the impact of casting size on durability and reliability of real casting components.

Study of Defect Formation during Solution Treatment of 319S Thixocast Turbo Impellers

Turbocharger impellers undergo extreme cyclic speed conditions and thus fatigue fracture in service. Any kind of defects, even defects with sizes of tens of micrometres, can make significant impact on service life of the impellers. The alloy used for thixocast impellers is the aluminum alloy 319s. T61 heat treatment is used to improve mechanical properties. However, the solution treatment in the standard T61 heat treatment of the 319s alloy can induce incipient melting defects. This paper carried out systematic study of formation of defects caused by the incipient melting during solution treatment in the thixocast and heat treated impellers, using optical and scanning electron microscope. Based on the study, the critical temperature of incipient melting is detected. An optimized two-stage solution treatment is therefore proposed.

Casting and Heat Treatment of Turbocharger Impellers Thixocast from Alloy 201

Commercial semi-solid cast impellers are produced from Al-Si-Cu alloys heat treated to the T6 temper. The study described in this paper involved the identification of casting and heat treatment parameters to produce semi-solid processed turbocharger impellers from a silicon-free, higher strength 201 alloy. Casting parameters were identified which minimized hot tearing in the alloy 201 impellers. A series of heat treatment studies were performed to determine optimum heat treatment parameters. The T71 temper was identified as the preferred heat treatment condition to produce high strength as well as superior elongation. The results from mechanical property measurements conducted on the T71 heat treated impellers are reported. Optical and scanning electron microscopy (SEM) were also used to characterize the microstructure of alloy 201 impellers before and after heat treatment, and representative microstructures are presented.

High-quality aluminum turbocharger impellers produced by thixocasting

The thixocasting process was chosen to produce the impellers as it is capable of producing castings with extremely high internal quality. Slugs cut from the DC cast bars are re-heated to the semi-solid casting temperature, and a specially-designed runner and gating system is used to prevent oxide from the surface of the slugs from becoming incorporated into the impeller. The technology used to produce the semi-solid impellers is described in detail. The semi-solid cast impellers, produced from an Al-Si-Mg-Cu alloy, are heat treated to the T6 temper. Results from testing are presented demonstrating that the impellers are free of porosity and other internal defects. Both mechanical property and fatigue data are presented showing that the semi-solid impellers have better properties than impellers produced by conventional casting and similar properties to forged and machined impellers. A short study is also described which identified suitable processing parameters to minimize hot tearing in the complex-shaped turbocharger impellers semi-solid cast from alloy 201. The surfaces of the impellers were examined using penetrant testing, and the results of modifying processing parameters on the propensity for surface cracking are presented. An aging study was performed to identify optimum mechanical strength.

Novel Method for Casting High Quality Aluminum Turbocharger Impellers

Novel Method for Casting High Quality Aluminum Turbocharger Impellers

427 スプレイフォーミング法による急冷凝固耐熱アルミニウム合金の開発(軽量化・高強度化材料(2))

The spray forming method is a rapid solidification technique for the deposit of molten metal using inert gas. Adoption of this method enables a reduction in manufacturing steps compared to the conventional powder sintering method, as well as allowing the manufacture of large-sized material. In the context of turbochargers for diesel engines, improved heat resistance for aluminum impellers is an issue under consideration due to requirements for lower energy consumption and higher output, i. e. , higher pressure power ratios. This paper presents the relationship between the strength properties and material structure of a heat-resistant Al-Fe alloy manufactured using the spray forming method, as well as the possibility of application for turbocharger impellers.

Numerical and Experimental Study of Unsteady Flow Field and Vibration in Radial Inflow Turbines

The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only a few investigations relating to unsteady aerodynamic forces in radial turbines have been presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut fu¨r Thermische Stro¨mungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high-pressure, high-temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser-Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase-resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier–Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated. [S0889-504X(00)01402-1]